Geosynthetic clay liner with modified edges for improved sealing

ABSTRACT

A clay liner is provided for use in constructing low permeability barriers in the bottom of landfills and man-made bodies of water. The liner is provided in the form of a layer of bentonite preferably disposed between a primary carrier sheet and a cover sheet. At least one outer edge of either the cover sheet or the primary carrier sheet is made from a material that allows substantial bentonite migration through or includes a slit that enables bentonite to migrate through while the remaining areas of the cover sheet or primary carrier sheet are fabricated from a fabric that does not permit substantial bentonite migration. When two liners are disposed adjacent to each other in the bottom of the landfill or pond, the two liners are overlapped so that the more open portion of one liner engages the adjacent liner. Upon activation, the bentonite migrates through the more open fabric to create a seal between the two adjacent liners. The result is a self-sealing geosynthetic clay liner system.

This is a continuation-in-part of application Ser. No. 08/006,222, filedJan. 19, 1993, now U.S. Pat. No. 5,350,255.

This invention relates generally to an improved liner used to create alow permeability barrier in the bottom of landfills and man-made bodiesof water such as man-made lakes and man-made ponds. More specifically,this invention relates to an improved clay liner for landfills and pondsmade with two sheets and a layer of bentonite suspended therebetween. Atleast one of the sheets, either the carrier sheet or the cover sheet,includes at least one longitudinal outer section that allows bentonitemigration through it. The structure of the outer longitudinal sectionallows for increased migration of activated bentonite and allows theouter longitudinal section of the clay liner to effectively seal with anouter section of an adjacent clay liner.

BACKGROUND OF THE INVENTION

The present invention relates to clay liners which are used to form avery low permeability barrier. The specific problem addressed by thepresent invention is how to create a seal between adjacent clay linersto provide a continuous and low permeability clay barrier.

A low permeability barrier is required in the construction of landfillsin order to retain any liquid, known as leachate, contained within thewaste material and keep the leachate out of the water table. Further, alow permeability bottom barrier is required in the construction of manyman-made lakes and ponds to preclude water loss through seepage.

The use of bentonite to create a low permeability barrier in landfillsand ponds is well known. Bentonite is a clay material which occursnaturally and it expands upon being exposed to or activated by water.When the bentonite absorbs water and expands, it is capable of forming abarrier with low permeability to fluid migration if the bentonite isproperly contained.

Geosynthetic clay liners may be made with one or two sheets. The primarybacking or carrier sheet is normally the more durable material and isoften disposed below the bentonite layer when installed in the landfill.The cover sheet, also referred to as scrim, is normally less durablethan the carrier sheet. Upon installation, the cover sheet may face upor down and the carrier sheet may face up or down, depending upon thespecific design of the landfill. A layer of bentonite supported by atleast one carrier sheet or disposed between two sheets (cover sheet andcarrier sheet) is often referred to as a geosynthetic clay liner or GCL.

Workers will spread rolls of geosynthetic clay liners out over the areato be covered in a manner similar to the installation of carpet. In thepast, in order to effectuate a seal between adjacent liners, it has beennecessary to overlap adjacent rolls of liner material. In liners wherethe bentonite is suspended between two sheets by a needle-punchingprocess, the seams must be augmented with granular bentonite, or othermeans, or liquids will leak downward at the seams created betweenadjacent rolls of liner material. The augmentation with granularbentonite (or other means) constitutes an extra installation step andtherefore is costly in terms of time and money. Further, these seamaugmentation procedures are dependant upon the construction crewfollowing exacting installation procedures to effectuate a reliableseam.

In order for the activated bentonite to create a low permeabilitybarrier, it must be properly contained. The bentonite may be containedbetween two sheets, a carrier sheet and a cover sheet. The bentonite maybe held in place by glue applied to the carrier sheet or byneedle-punching the cover sheet to the carrier sheet or by stitching thecarrier sheet to the cover sheet or a combination thereof. The sheetsmay be manufactured from durable woven or non-woven materials or sheetsthat do not permit the bentonite to substantially migrate through thematerial. By properly containing the bentonite between two sheets thatdo not allow for substantial migration of the bentonite, the bentoniteis properly contained and, upon activation by water, the bentonite willswell and form a low permeability barrier between the two sheets.

Depending on the construction of the fabrics or materials used, thelower or bottom sheet may not allow for the bentonite to migrate throughto create a low permeability seam and simply overlapping adjacent linersmay not insure that the proper seal will be attained between the twoadjacent liners. In other words, laying an outer portion of the lowersheet of one liner on top of an outer portion of an upper sheet of anadjacent liner may not insure that a proper seal will be obtainedbetween the two liners. In the case where the materials contained withinthe landfill include hazardous waste, a lack of a proper seal willresult in leakage and will have serious ramifications.

Thus, there is a need for a bentonite clay liner, or a geosynthetic clayliner, that will ensure that a proper seal is obtained between twoadjacent liners as the liners are installed in the bottom of a landfillor pond. Preferably, the geosynthetic clay liners should be self-sealingwhen adjacent liners are overlapped thereby insuring that no "seams"will leak and further providing a geosynthetic liner system that isquickly and efficiently installed.

BRIEF DESCRIPTION OF THE INVENTION

A geosynthetic clay liner is provided that includes a layer of bentonitedisposed between a carrier sheet and a cover sheet. At least one sheet,either the carrier sheet or the cover sheet, is made of material withtwo distinct structures. The central portion or the bulk portion of thesheet precludes the substantial migration of bentonite through it andcontains the bentonite. The central portion includes a relatively closedstructure and therefore precludes substantial bentonite migrationthrough it. In contrast, at least one longitudinal outer edge orlongitudinal section of the said sheet has a more open structure andallows substantially more bentonite to migrate through it. The more openouter longitudinal section is the overlap section which will be laid ontop of or underneath an adjacent geosynthetic clay liner to create aseal between adjacent liners.

The more open structure of the outer section may be in the form of amore open weave, a series of perforations, a slit, cut or groove orother means for enabling bentonite to migrate through the sheet so itcan form a seal with our adjacent liner.

In one embodiment, at least one sheet is fabricated from non-wovenmaterial. A slit is cut or melted adjacent to an outer edge of thenon-woven sheet thereby providing the more open outer longitudinalsection next to the more closed central portion. In contrast, if thesheet is fabricated from woven material, then the preferred structureincludes a tightly woven central portion with a loosely woven outerlongitudinal section. Either way, bentonite is permitted to migratethrough a slit or through an open weave so it can effectuate a seal withan adjacent, overlapping liner.

Upon activation, the bentonite swells to form the low permeabilitybarrier. Because the central portion of one sheet includes a closedstructure, the bentonite is substantially contained and does not migratethrough the central portion of the sheet. However, because the outerlongitudinal section, or the overlap section, is more open or is looselywoven or includes a longitudinal slit or groove, the activatingbentonite substantially migrates through it and engages the adjacentgeosynthetic clay liner that has been overlapped by the outerlongitudinal section or outer edge. The substantial migration of thebentonite through the longitudinal section ensures that an effectiveseal is created between one geosynthetic clay liner and an adjacentgeosynthetic clay liner.

As noted above, the open structure of the outer longitudinal section orouter edge may be obtained by cutting or melting a slit along the outeredge of non-woven fabric, or, if woven fabric is used, by employing alooser weave (i.e. lower warp yarn count) than the closed structure ofthe central portion (high warp yarn count). Also, the more openstructure of the outer longitudinal section may be obtained by aneedle-punching or perforation process that creates a structure thatwill allow for substantial bentonite migration through it. Theneedle-punching and perforation methods are especially adaptable forgeosynthetic clay liners made without gluing the bentonite to one of thesheets (i.e. a needle-punched liner). Both the loosely woven andneedle-punched/perforation sections are referred to as the open sectionsbelow and the term "open" is meant to indicate ease of substantialbentonite migration. In contrast, the term "closed" is meant to indicatea low permeability structure that does not permit substantial bentonitemigration.

In terms of industry nomenclature, the terms primary textile and primarycarrier sheet are often used interchangeably. Unless otherwise noted,the primary carrier will refer to the more durable textile or sheet of ageosynthetic liner and is normally disposed downward upon installation.However, primary carrier sheets may be disposed upward uponinstallation, depending upon the intended purpose of the geosyntheticliner. Also, the terms secondary textile, secondary carrier sheet, scrimand cover sheet may also be used interchangeably. Unless otherwise note,the term cover sheet will refer to the textile or sheet that isconnected or otherwise attached to the primary carrier sheet with alayer of bentonite disposed therebetween. Normally, the cover sheet isdisposed upward upon installation, but may also be disposed downward,depending upon the intended purpose of the geosynthetic liner.

Assuming the cover sheet is disposed upward when installed, if the moreopen longitudinal section is provided at an outer edge of the coversheet, the outer edge of the cover sheet is disposed beneath an outeredge of an adjacent geosynthetic clay liner so that the more openlongitudinal section engages at least an outer edge of the adjacentliner. As the bentonite is activated, it will migrate upward to engageand seal with the underside of the primary carrier sheet of the adjacentliner.

In contrast, if the more open longitudinal section or slit is providedat an outer edge of a lower primary carrier sheet, the outer edge of thelower primary carrier sheet is disposed on top of an outer edge of anadjacent geosynthetic clay liner so that the more open longitudinalsection or slit engages at least an upper outer edge of the cover sheetof the adjacent liner. The bentonite, upon activation, will migratedownward through the longitudinal section or slit and engage a portionof a cover sheet of an adjacent geosynthetic clay liner. Any "seam"between the two adjacent geosynthetic clay liners is eliminated by thebentonite migrating through the more open longitudinal section or slitand engaging the adjacent geosynthetic clay liner.

More than one open longitudinal section or slit may be provided witheach geosynthetic clay liner. For example, a more open longitudinalsection or slit may be provided at each outer edge of the upper coversheet. In this case, only half of the liners will require the more openlongitudinal sections or slits and liners without the more openlongitudinal sections or slits would be disposed on either side andoverlap on top of the more open longitudinal sections or slits. Two openlongitudinal sections or slits may also be disposed at either edge ofthe lower carrier sheets and these longitudinal sections or slits wouldoverlap on top of adjacent cover sheets with or without openlongitudinal sections or slits. The more open longitudinal section orslit may be disposed at any edge of the geosynthetic clay liner and morethan one open longitudinal section or slit may be provided with eachgeosynthetic clay liner.

One preferred method for creating a continuous bentonite layer that issubstantially impervious to migrating liquids includes the use ofgeosynthetic clay liners as described above. If the liners include onlyone open longitudinal section disposed on an outer edge of the uppercover sheet, each liner is rolled out and the open longitudinal sectionis overlapped, or disposed below, an outer edge of a lower carrier sheetof an adjacent geosynthetic clay liner. Because only one openlongitudinal section is provided with each geosynthetic clay liner, each"seam" will include only one open longitudinal section.

With respect to the installation of the slits or cuts into a non-wovensheet, the slit may be installed with a cutting blade or the sheet maybe melted if the non-woven sheet is made of a material that is easilymelted, such as polyethylene.

It is therefore an object of the present invention to provide animproved geosynthetic clay liner with at least one self-sealing outeredge.

It is also an object of the present invention to provide an improvedgeosynthetic clay liner that will seal with an adjacent geosyntheticclay liner, thereby avoiding leakage at the seams between adjacentliners.

Yet another object of the present invention is to provide an improvedsystem for providing a low permeability layer of bentonite at the bottomof landfills and man-made bodies of water.

Still another object of the present invention is to provide an improvedmethod for constructing a low permeability bentonite layer in the bottomof landfills and man-made bodies of water.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention is illustrated more or less diagrammatically in theaccompanying drawings, wherein:

FIG. 1 is a perspective view of a geosynthetic clay liner made inaccordance with the present invention;

FIG. 2 is a front sectional view showing an installation of threeadjacent geosynthetic clay liners made in accordance to the presentinvention;

FIG. 3 is another front sectional view of an installation of threeadjacent geosynthetic clay liners made in accordance with the presentinvention;

FIG. 4 is another front sectional view showing an installation of threegeosynthetic clay liners made in accordance with the present invention;

FIG. 5 is another front sectional view of an installation of threegeosynthetic clay liners made in accordance with the present invention;

FIG. 6 is another front sectional view of the preferred installation ofthree geosynthetic clay liners made in accordance with the presentinvention;

FIG. 7 is another front sectional view of an installation of threegeosynthetic clay liners made in accordance with the present invention;

FIG. 8 is an alternative installation scheme used with the geosyntheticclay liners shown in FIG. 7;

FIG. 9 is a perspective view of yet another geosynthetic clay liner madein accordance with the present invention;

FIG. 10 is a front sectional view showing an installation of threeadjacent geosynthetic clay liners made in accordance with the presentinvention;

FIG. 11 is another front sectional view of an installation of threeadjacent geosynthetic clay liners made in accordance with the presentinvention;

FIG. 12 is another front sectional view of an installation of threeadjacent geosynthetic clay liners made in accordance with the presentinvention;

FIG. 13 is another front sectional view of an installation of threeadjacent geosynthetic clay liners made in accordance with the presentinvention;

FIG. 14 is another front sectional view of an installation of threeadjacent geosynthetic clay liners made in accordance with the presentinvention;

FIG. 15 is another front sectional view of an installation of threeadjacent geosynthetic clay liners made in accordance with the presentinvention; and

FIG. 16 is another front sectional view of an installation of threeadjacent geosynthetic clay liners made in accordance with the presentinvention.

It should be understood that the drawings are not necessarily to scaleand that the embodiments are sometimes illustrated by graphic symbols,phantom lines, diagrammatic representations and fragmentary views. Incertain instances, details which are not necessary for an understandingof the present invention or which render other details difficult toperceive may have been omitted. It should be understood, of course, thatthe invention is not necessarily limited to the particular embodimentsillustrated herein.

DETAILED DESCRIPTION OF THE INVENTION

Like reference numerals will be used to refer to like or similar partsfrom Figure to Figure in the following descriptions of the drawings.

FIG. 1 is an illustration of the geosynthetic clay liner 10 including anupper cover sheet 11, a bentonite layer 12 and a lower carrier sheet 13.All of the Figures and the description below depict the cover sheet asthe top sheet when installed and the carrier sheet as the bottom sheetwhen installed. It will be understood that the installation design maywarrant reversal of this configuration and the present invention appliesequally to both configurations.

The upper cover sheet 11 includes a central portion, indicated generallyat 14 and an outer longitudinal section, indicated generally at 15. Thereader will note that the central portion 14 is more tightly woven orhas a more closed structure and the outer longitudinal section 15 has amore open structure. The central portion 14 has a higher warp count thanthe warp count of the outer longitudinal section 15 or the longitudinalsection 15 is perforated or needle-punched and the central portion 14 isnot. The more open longitudinal section 15 provides for substantialmigration of the bentonite 12 up through the longitudinal section 15upon activation of the bentonite 12 with an activating fluid, such aswater.

An illustration of the installation of the geosynthetic clay liner 10,like the one shown in FIG. 1, is illustrated in FIG. 2. A firstgeosynthetic clay liner 10a is laid down on the bottom of a landfill orpond (not shown). The geosynthetic clay liner 10a includes an uppercover sheet 11 that includes a more open longitudinal section 15. Asecond geosynthetic clay liner 10b is laid down with an outer end 16overlapping the more open longitudinal section 15. A third geosyntheticclay liner 10c is laid down with an outer portion 16 disposed on top ofthe more open longitudinal section 15 of the geosynthetic liner 10b.

Upon activation by water, the bentonite 12 migrates upward through themore open longitudinal sections 15 and engages the lower carrier sheets13 of the geosynthetic clay liners 10c and 10b as illustrated in FIG. 2.The expanding and migrating bentonite 12 forms a seal between thebentonite layers disposed between the cover sheet 11 and carrier sheet13 of one geosynthetic clay liner such as 10a, 10b and the lower carriersheet 13 of the adjacent clay liner such as 10b, 10c.

In FIG. 2, the more open longitudinal section 15 is provided at oneouter edge of each upper cover sheet 11. In FIG. 3, the more openlongitudinal section 15 are provided at an outer edge of each lowercarrier sheet 13. Referring to FIGS. 2-6 collectively, in order toaffect a seal between the geosynthetic clay liners 10 (actually 10athrough 10n), the more open longitudinal sections 15 must be arranged sothat they engage the overlapping portion 16 of an adjacent carrier sheetas shown in FIGS. 2 through 6.

FIGS. 4 and 5 illustrate an alternative embodiment of the presentinvention where the liners 10i through 10j include an overlap sheet orextension 17. The overlap sheets 17 are intended to prevent anysubstantial downward migration of the bentonite 12 which might clog orotherwise interfere with a drainage system disposed below thegeosynthetic clay liners 10.

For example, referring to FIG. 4, the bentonite 12, upon activation,will migrate downward through the more open longitudinal sections 15 andengage the outer ends 16 of the adjacent geosynthetic clay liners 10h,10g. Any excess bentonite 12 migrating through the longitudinal sections15 and over the outer overlapping edge 16 will be contained by theoverlap sheet 17. The overlap sheet 17 is an extension of the lowercarrier sheet 13 or may be a separate sheet attached thereto.Preferably, the overlap sheets 17 are made from a material that allowslittle migration of bentonite 12. FIG. 5 illustrates a variation of theconcept illustrated in FIG. 4, only with overlap extensions 17 disposedon both outer edges of each lower carrier sheet 13. The bentonite 12 ofthe liners 10j, 10k, 10l will migrate through the loosely wovenlongitudinal sections 15. Any bentonite 12 migrating out of the outeredges 17a will be contained by the overlapping sections 17.

FIG. 6 illustrates a variation of the concept illustrated in FIG. 2,only with loosely woven longitudinal sections 15 disposed on both edges15 of each cover sheet 11 of each overlapping geosynthetic clay liner10m, 10n, 10o.

FIG. 7 is an illustration of a liner system incorporating geosyntheticclay liners 20 equipped with more open longitudinal sections 15 disposedon both outer edges of both the upper cover sheet 11 and the lowerprimary carrier sheet 13. FIG. 8 is an illustration of an alternativeinstallation scheme used with the geosynthetic liners 20 first shown inFIG. 7.

The preferred material for fabrication of the carrier sheets is fabricwoven from slit film polypropylene fibers. The slit film fibers may havea width from 1/32 to 1/8-inch. The longitudinal sections should be atleast 3 inches wide and normally not more than 24 inches wide andpreferably from about 6 to about 12 inches wide. The overlap sheetsshould be at least 6 inches wide and no more than 3 feet wide andpreferably from about 18 inches to about 2 feet wide.

FIG. 9 illustrates an additional liner 30 that employs a differentscheme for bentonite migration at an outer longitudinal section or outeredge to effectuate a seal between the liner 30 and an adjacent liner.Specifically, the liner 30 includes a slit 31 disposed along an outeredge of the liner. The bentonite 12 will migrate upward through the slit31 to engage an underside of an adjacent liner as shown in FIG. 10.Still referring to FIG. 1, the slit 31 may be easily cut into the coversheet 11 if the cover sheet 11 is fabricated from non-woven material. Anadditional method of disposing the slit 31 in the non-woven cover sheet11 would be to melt the slit 31 into the cover sheet 11 assuming thecover sheet 11 is fabricated from a low-melting point material, such aspolypropylene. In fact, polypropylene is a preferred material for thefabrication of non-woven geotextile sheets and therefore it isanticipated that melting the slit 31 in a polypropylene non-woven coversheet 11 will be as feasible a method as cutting the slit 31 into thecover sheet 11.

Turning to FIG. 10, an installation of three liners 30a-30c isillustrated. A first geosynthetic clay liner 30a is laid down on thebottom of a landfill or pond (not shown). The geosynthetic clay 30aincludes an upper cover sheet 11 with a slit 31 disposed parallel to anouter edge thereof. An outer edge of the adjacent liner 30b is laid ontop of the slit 31 of the liner 30a. Upon activation, some of thebentonite 12 will migrate upward through the slit 31 to engage an outeredge of the primary carrier sheet 13 of the adjacent liner.

In FIG. 11, the configuration of the liners 30d-30f is reversed from theconfiguration of the liners 30a-30c as shown in FIG. 10. That is, theprimary carrier sheet 13 is fabricated from non-woven material andincludes a slit 31. Therefore, bentonite 12 migrates downward throughthe slit 31 disposed in the non-woven primary carrier sheet 13 where itwill bond with the cover sheet of an adjacent liner. In theconfiguration shown in FIG. 11, the cover sheet 11 may be fabricatedfrom woven or non-woven materials. However, because a slit 31 is noteasily cut or burned into a woven material, the primary carrier sheet 13is preferably fabricated from non-woven material, such as polypropyleneor other low-melting point materials which will become apparent to thoseskilled in the art.

FIG. 12 is an illustration of the configuration shown in FIG. 11 buteach carrier sheet includes an overlap sheet 17 to preclude any downwardmigration of bentonite 12 past the liners 30g-30i as illustrated in FIG.4 with respect to the liners 10g-10i.

FIGS. 13 and 14 illustrate the use of two slits 31a, 31b disposed alongan outer edge of each cover sheet 11. The parallel slits 31a, 31b may beeither cut or melted into the non-woven cover sheet 11 with parallelcutting blades or parallel melting instruments. It will also be noted inFIG. 13 that the primary carrier sheet 13 of the liners 30j-30l includedual extension flaps 17 to prevent the downward migration of bentonite12 below the liners 30j-30l. In FIG. 14, the liners 30m-30o include thedual slits 31a, 31b but do not include any extension flaps.

FIGS. 15 and 16 disclose liners with slits or grooves 31 disposed inboth the cover sheet 11 and primary carrier sheet 13. For example, inFIG. 15, the liners 30p-30r include a pair of upper slits 31c and lowerslits 31d so that the bentonite 12 will migrate both upward through thecover sheet 11 and downward through the primary carrier sheet 13.Finally, FIG. 16 discloses the use of adjacent slits 31a, 31b disposedalong each outer edge of the cover sheet 11 as well as adjacent slits31e, 31f disposed along each outer edge of the primary carrier sheet 13as illustrated with respect to the liners 30s-30u.

As noted above, the preferred material for use in constructing non-wovensheets that will accommodate one or more slits is polypropylene. Onepreferred material for the woven geotextile sheets is known as Amoco4005. Amoco 4005 is a slit film woven polypropylene fabric that has beenneedle-punched with one to one and one-half ounces per square yard ofstaple polypropylene fibers of approximately 6 denier. The constructionof the weave is approximately 24 warp and 12 weft slit film fibers perinch in a flat woven pattern. This fabric has been found to be aneffective primary carrier sheet or primary carrier 13. A looser, moreopen weave is employed for the longitudinal section 15 if it is disposedat an outer edge of a primary carrier sheet 13 made with Amoco 4005.

By using the geosynthetic clay liners 10, 20 or 30 of the presentinvention, geotechnical engineers are ensured that minimal leakage willoccur in the clay barrier provided by the bentonite 12. Construction ofthe barrier at the bottom of landfills and man-made bodies of water willbe fast and efficient because no additional effort is required to sealthe seams between two adjacent liners. The geosynthetic clay liners ofthe present invention are self-sealing at the seams between adjacentoverlapping liners.

While only a selection of specific embodiments of the present inventionhas been illustrated and described, it will at once be apparent to thoseskilled in the art that variations may be made within the spirit andscope of the invention. Accordingly, it is intended that the scope ofthe invention be limited solely by the scope of the hereafter appendedclaims and not by any specific wording and the foregoing description.

We claim:
 1. A geosynthetic clay liner comprising:a clay layer disposedbetween a primary geosynthetic carrier sheet and a geosynthetic coversheet, the cover sheet including a central portion having a more closedstructure than a longitudinal outer edge section of the cover sheet, andsaid longitudinal edge section having a more open structure than saidcentral portion of the cover sheet, said more open structure provided bya slit extending along said longitudinal outer edge section, the slitallowing substantial migration of activated clay through the slit, andactivated clay migrating through the slit to create an activated clayseal between the cover sheet of the geosynthetic clay liner and aprimary carrier sheet of an adjacent geosynthetic clay liner disposedbelow the slit.
 2. The clay liner of claim 1, wherein the longitudinalouter edge section of the cover sheet includes two parallel slits. 3.The clay liner of claim 1, wherein the cover sheet includes two opposedlongitudinal edge sections, each having a slit therein.
 4. The clayliner of claim 1, wherein the cover sheet is fabricated from non-wovenmaterial.
 5. A geosynthetic clay liner comprising:a clay layer disposedbetween a primary geosynthetic carrier sheet and a geosynthetic coversheet, the primary carrier sheet including a central portion having amore closed structure than a longitudinal outer edge section of theprimary carrier sheet, and said longitudinal edge section having a moreopen structure than said central portion of the primary carrier sheet,said more open structure provided by a slit extending along saidlongitudinal outer edge section, the slit allowing substantial migrationof activated clay through the slit, and activated clay migrating throughthe slit to create an activated clay seal between the primary carriersheet of the geosynthetic clay liner and a cover sheet of an adjacentgeosynthetic clay liner disposed above the slit.
 6. The geosyntheticclay liner of claim 5, wherein the primary carrier sheet includes twoopposed longitudinal edge sections, each having a slit therein.
 7. Thegeosynthetic clay liner of claim 5, wherein the cover sheet includes twoopposed longitudinal edge sections, each having a slit therein.
 8. Thegeosynthetic clay liner of claim 5, wherein the primary carrier sheet isfabricated from non-woven material.
 9. A geosynthetic clay liner for usein forming a continuous clay layer that is substantially impervious tofluids, the geosynthetic clay liner comprising:a cover sheet made ofnon-woven geosynthetic fabric, a primary carrier sheet made of wovengeosynthetic fabric, at least one clay layer disposed between the coversheet and the primary carrier sheet, the clay layer, the cover sheet andthe primary carrier sheet having outer edges in matching registry, thecover sheet including a central portion having a more closed structurethan a longitudinal outer edge section of the cover sheet, and saidlongitudinal edge section having a more open structure than said centralportion of the cover sheet, said more open structure provided by atleast one slit extending along the outer edge thereof for overlappingsaid primary carrier sheet of an adjacent geosynthetic clay liner, andthe clay layer, after activation by an activating fluid, at leastpartially migrating upwardly through the slit of the cover sheet toengage the primary carrier sheet of the adjacent geosynthetic clay linerto provide an activated clay seal between the slit of the cover sheetand the primary carrier sheet of the adjacent geosynthetic clay liner.10. A geosynthetic clay liner for use in forming a continuous clay layerthat is substantially impervious to fluids, the geosynthetic clay linercomprising:a cover sheet made of woven geosynthetic fabric, a primarycarrier sheet made of non-woven geosynthetic fabric, at least one claylayer disposed between the cover sheet and the primary carrier sheet,the clay layer, the cover sheet and the primary carrier sheet havingouter edges in matching registry, the primary carrier sheet including acentral portion having a more closed structure than a longitudinal outeredge section of the primary carrier sheet, and said longitudinal edgesection having a more open structure than said central portion of theprimary carrier sheet, said more open structure provided by at least oneslit extending along the outer edge thereof for overlapping said coversheet of an adjacent geosynthetic clay liner, and the clay layer, afteractivation by an activating fluid, at least partially migratingdownwardly through the slit of the primary carrier sheet to engage thecover sheet of the adjacent geosynthetic clay liner to provide anactivated clay seal between the slit of the primary carrier sheet andthe cover sheet of the adjacent geosynthetic clay liner.
 11. Ageosynthetic clay liner for use in forming a continuous clay layer thatis substantially impervious to fluids, the geosynthetic clay linercomprising:a clay layer disposed between at least one primarygeosynthetic carrier sheet and at least one geosynthetic cover sheet,the cover sheet, the clay layer and the primary carrier sheet formingthe geosynthetic clay liner, the geosynthetic clay liner includinglongitudinal outer edges, said primary carrier sheet including a centralportion having a more closed structure than a longitudinal outer edgesection of the primary carrier sheet, and said longitudinal edge sectionhaving a more open structure than said central portion of the primarycarrier sheet, said more open structure provided by at least one slitdisposed in said longitudinal outer edge of the primary carrier sheet,the slit permitting substantial migration of activated clay through theslit, the slit engaging at least a portion of an adjacent geosyntheticclay liner, and the activated clay migrating through the slit to createa seal between two adjacent geosynthetic clay liners by creating anactivated clay seal between the slit of one geosynthetic clay liner andan adjacent geosynthetic clay liner.
 12. The clay liner of claim 11,wherein the primary carrier sheet is fabricated from non-woven material.13. A geosynthetic clay liner for use in forming a continuous clay layerthat is substantially impervious to fluids the geosynthetic clay linercomprising:a clay layer disposed between at least one primarygeosynthetic carrier sheet and at least one geosynthetic cover sheet,the cover sheet, the clay layer and the primary carrier sheet formingthe geosynthetic clay liner, the geosynthetic clay liner includinglongitudinal outer edges, said cover sheet including a central portionhaving a more closed structure than a longitudinal outer edge section ofthe cover sheet, and said longitudinal edge section having a more openstructure than said central portion of the cover sheet, said more openstructure provided by at least one slit disposed in said longitudinalouter edge of the cover sheet, the slit permitting substantial migrationof activated clay through the slit, the slit engaging at least a portionof an adjacent geosynthetic clay liner, and the activated clay migratingthrough the slit to create a seal between two adjacent geosynthetic clayliners by creating an activated clay seal between the slit of onegeosynthetic clay liner and an adjacent geosynthetic clay liner.
 14. Theclay liner of claim 13, wherein the cover sheet is fabricated fromnon-woven material.
 15. A lining system for containing liquid, thesystem comprising:a plurality of geosynthetic clay liners, eachgeosynthetic clay liner including at least one clay layer, each claylayer disposed between at least one primary geosynthetic carrier sheetand at least one geosynthetic cover sheet, each primary carrier sheetincluding a central portion having a more closed structure than alongitudinal outer edge section of the primary carrier sheet, and saidlongitudinal edge section having a more open structure than said centralportion of the primary carrier sheet, said more open structure providedby at least one slit disposed in said longitudinal outer edge thereof,the slit of one geosynthetic clay liner engaging at least a portion ofan adjacent geosynthetic clay liner, the slit of each primary carriersheet permitting substantial migration of activated clay through theslit, the slit engaging at least a portion of an adjacent geosyntheticclay liner, and activated clay migrating through the slit creating aseal between two adjacent geosynthetic clay liners by creating anactivated clay seal between the slit of one geosynthetic clay liner andthe cover sheet of an adjacent geosynthetic clay liner.
 16. A liningsystem for containing liquid, the system comprising:a plurality ofgeosynthetic clay liners, each geosynthetic clay liner including atleast one clay layer, each clay layer disposed between at least oneprimary geosynthetic carrier sheet and at least one geosynthetic coversheet, each cover sheet including a central portion having a more closedstructure than a longitudinal outer edge section of the cover sheet, andsaid longitudinal edge section having a more open structure than saidcentral portion of the cover sheet, said more open structure provided byat least one slit disposed along an outer edge thereof, the slit of onegeosynthetic clay liner engaging at least a portion of an adjacentgeosynthetic clay liner, the slit of each cover sheet permittingsubstantial migration of activated clay through the slit, the slitengaging at least a portion of an adjacent geosynthetic clay liner, andactivated clay migrating through each slit creating a seal between twoadjacent geosynthetic clay liners by creating an activated clay sealbetween the slit of one geosynthetic clay liner and the primary carriersheet of an adjacent geosynthetic clay liner.
 17. A method formanufacturing a continuous clay layer that is substantially imperviousto migrating liquids, the method comprising:covering an area with aplurality of geosynthetic clay liners, each geosynthetic clay linerincludinga geosynthetic cover sheet, a geosynthetic primary carriersheet and at least one clay layer disposed therebetween, the clay layer,the cover sheet and the primary carrier sheet having longitudinal outeredges in matching registry, the cover sheet including a central portionhaving a more closed structure than a longitudinal outer edge section ofthe cover sheet, and said longitudinal edge section having a more openstructure than said central portion of the cover sheet, said more openstructure provided by a slit disposed along an outer edge thereof foroverlapping a primary carrier sheet of an adjacent geosynthetic clayliner, the slit of the cover sheet allowing the clay layer, afteractivation by an activating fluid, to at least partially migrateupwardly through the slit of the cover sheet to engage the primarycarrier sheet of the adjacent geosynthetic clay liner disposed above theslit of the cover sheet to provide an activated clay seal between theslit of the cover sheet and the primary carrier sheet of the adjacentgeosynthetic clay liner, engaging the slit of each cover sheet with atleast a portion of a primary carrier sheet of an adjacent geosyntheticclay liner, and activating the clay layers with an activating liquid topermit upward migration of activated clay through the slit of the coversheet to engage the portion of the primary carrier sheet of the adjacentgeosynthetic clay layer.
 18. A method for providing a continuous claylayer that is substantially impervious to migrating liquids, the methodcomprising:covering an area with a plurality of geosynthetic clayliners, each geosynthetic clay liner includinggeosynthetic cover sheet,a geosynthetic primary carrier sheet and at least one clay layerdisposed therebetween, the clay layer, the cover sheet and the primarycarrier sheet having longitudinal outer edges in matching registry, theprimary carrier sheet including a central portion having a more closedstructure than a longitudinal outer edge section of the primary carriersheet, and said longitudinal edge section having a more open structurethan said central portion of the primary carrier sheet, said more openstructure provided by a slit disposed along said longitudinal outer edgethereof for overlapping a cover sheet of an adjacent geosynthetic clayliner, the slit allowing the clay layer, after activation by anactivating fluid, to at least partially migrate downward through theslit of the primary carrier sheet to engage the cover sheet of theadjacent geosynthetic clay liner disposed below the slit of the primarycarrier sheet to provide an activated clay seal between the slit of theprimary carrier sheet and the cover sheet of the adjacent geosyntheticclay liner, engaging a slit of each primary carrier sheet with at leasta portion of a cover sheet of an adjacent geosynthetic clay liner, andactivating the clay layers with an activating liquid to permit downwardmigration of activated clay through the slit of the primary carriersheet to engage the portion of the cover sheet of the adjacentgeosynthetic clay liner.